1. Field of the Invention
The present invention relates to an image sensor, and more particularly, to an image sensor and an amplifying/digitizing circuit thereof.
2. Description of the Prior Art
In an image system, an analog-to-digital converter (ADC) is indispensable for converting a sensed signal of an analog format into a digital format, and is broadly used in various applications, such as a CMOS Image Sensor (CIS) system. The ADCs can be divided into flash ADCs, ramp ADCs, pipelined ADCs, and successive approximation ADCs, etc. according to corresponding circuit structures.
Please refer to FIG. 1. FIG. 1 is a conventional image sensor system 100, which includes a sensor array 110, a column amplifier 120, an ADC 130, and an image processor 140. The signals from the sensor array 110 are first amplified by the column amplifiers 120 and then converted into digital form by the ADC 130. Conventionally, the image sensor system 100 may use a ramp ADC as the ADC 130.
Due to the existing ADC structures lack the amplification functionality, the conventional image sensor system 100 has to adopt an amplification circuit as the column amplifier 120 for improving the SNR and promoting the image quality of the image sensor system 100.
In order to minimize the chip area and enhance the performance, manufacturers are dedicated to design new circuits to achieve the goals.